The present application relates to a material, and to a heating cable which includes the material.
Heating cables are well known, and are used for example to heat pipes in chemical processing plants. Typically, a heating cable is attached along the exterior of a pipe which is exposed to the components. Often, the heating cable is attached to a thermostat, and is activated by the thermostat when the temperature falls below a predetermined level. The heating cable acts to warm the pipe, thereby ensuring that the temperature of the pipe remains sufficiently high that the contents of the pipe do not become frozen or undergo other unwanted temperature related effects.
In recent years, heating cables have been manufactured which include a material having a positive temperature coefficient of resistance. This has the advantage that the heating cable is self regulating (when a constant voltage is applied across the heating cable). The current supplied to the heating cable will reduce as its temperature increases, thereby preventing the heating cable reaching an unwanted excessively high temperature. A problem associated with heating cables of this type is that they have a very low resistance when at low temperatures. This can cause an unwanted surge of current to pass through the heating cable when, for example, a power supply connected to the heating cable is turned on. Various mechanisms have been suggested to solve this problem.